Heat storage tank with improved heat insulating performance

ABSTRACT

A heat storage tank, comprises an inner cylinder  81  having a storage section  811  for storing liquid, an opening  812  at a lower position of the storage section  811  and a body  84  in which a liquid inflow channel  841  and a liquid outflow channel  842  are formed. The body blocks the opening  812.  When the inner diameter of the inner cylinder  81  is referred to as a tank inner diameter D and the vertical length of the storage section  811  is referred to as a tank height H, D/H≦0.5 holds. Therefore, the storage section  811  is elongated in the vertical direction and the distance between the body  84,  which is a main heat radiating portion, and the high temperature water region is increased and, as a result, the high temperature water region is extended in the vertical direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat storage tank for thermallyinsulating and storing a liquid and is effectively applied,particularly, to a cooling device of a water-cooled engine.

2. Description of the Related Art

Conventionally, a system in which a heat storage tank thermallyinsulates and stores high temperature engine cooling water in it andthen the thermally insulated cooling water is used for promoting warm-upof an engine when the engine is started next time (at a cold start) bycirculating the thermally insulated cooling water into the engine, or isused for immediately heating a vehicle compartment by supplying thethermally insulated cooling water to the heater core of a heating deviceof a vehicle is known (for example, refer to Patent document 1).

[Patent Document 1]

Japanese Unexamined Patent Publication (Kokai) No. 10-71840

Then, the heat insulation performance of a heat storage tank isparticularly regarded as an important factor and a further improvementof the heat insulation performance is required.

SUMMARY OF THE INVENTION

The above-mentioned point being taken into account, the object of thepresent invention is to improve the heat insulation performance of aheat storage tank.

In order to attain the above-mentioned object, a heat storage tankaccording to a first aspect of the present invention is characterized bycomprising an inner cylinder (81) having a storage section (811) forstoring liquid and an opening (812) at a lower position of the storagesection (811), an outer cylinder (82) accommodating the inner cylinder(81) therein and forming a thermally insulated space (83) between theinner cylinder (81) and itself, and a body (84) in which a liquid inflowchannel (841) and a liquid outflow channel (842) for causing the storagesection (811) to be communicated with the outside are formed and whichblocks the opening (812), wherein if it is assumed that the innerdiameter of the inner cylinder (81) is referred to as a tank innerdiameter D and the length of the storage section (811) in the verticaldirection is referred to as a tank height H in the heat storage tank inwhich the storage section (811) is a columnar space extending in thevertical direction, D/H≦0.5 holds.

According to this, as shown in FIG. 3, in the region where D/H≦0.5holds, the temperature of the water after being stored is high and ahigh heat-insulation performance can be obtained. This is because thestorage section is elongated in the vertical direction and the distancebetween the body, which is a main heat radiating portion, and the hightemperature water region (in the vicinity of the top end of the storagesection) is increased and therefore the high temperature water region isextended in the vertical direction.

When the inner diameter of the opening and the capacity of the storagesection are kept constant, as D/H is reduced, the tank inner diameter Dis reduced and the difference in dimension between the tank innerdiameter D and the inner diameter of the opening is reduced, therefore,the draw manufacturing performance of the inner cylinder is enhanced andit is possible to integrally form the inner cylinder by, for example, aspinning process.

In a second aspect according to the above-mentioned first aspect, it ispossible to use a heat storage tank for storing cooling water that hasrisen in temperature after cooling a water-cooled internal combustionengine (1) for a vehicle.

The symbols in the parenthesis attached to each means described aboveindicate a correspondence with a specific means in the embodiments to bedescribed later.

The present invention may be more fully understood from the descriptionof the preferred embodiments of the invention set forth below, togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic diagram of a cooling device for a water-cooledengine using a heat storage tank according to an embodiment of thepresent invention.

FIG. 2 is a section view of the heat storage tank in FIG. 1.

FIG. 3 is a diagram showing a relationship between the ratio (D/H) ofthe tank inner diameter to the tank height and the heat insulationperformance of the heat storage tank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is explained below. FIG. 1 is aschematic diagram of a cooling device for a water-cooled engine using aheat storage tank according to an embodiment and FIG. 2 is a sectionalview of the heat storage tank in FIG. 1.

In FIG. 1, the cooling device cools cooling water that has risen intemperature after cooling a water-cooled internal combustion engine(hereinafter, referred to as an engine) 1 of a vehicle, not shown,through a radiator 2, and comprises a main cooling water circuit 3 forcausing cooling water to flow between the engine 1 and the radiator 2and an electric water pump 4 for generating a cooling water flow.

A bypass circuit 5 for causing cooling water to flow while bypassing theradiator 2 is connected in parallel with the main cooling water circuit3. A thermostat 6 provided at the connection point of the main coolingwater circuit 3 and the bypass circuit 5 carries out switching controlbetween a case where the cooling water is caused to flow through thebypass circuit 5 and a case where the cooling water is caused to flowthrough the radiator 2. By the way, switching between the two circuits 3and 5 is normally controlled such that the cooling water flows throughthe radiator 2 when the cooling water temperature is equal to or higherthan about 80° C. and the cooling water flows through the bypass circuit5 when the temperature is lower than about 80° C.

A sub-cooling-water circuit 7 for causing the cooling water to flowwhile bypassing the main cooling water circuit 3 and the bypass circuit5 is connected in parallel to the main cooling water circuit 3 and thebypass circuit 5. The sub-cooling-water circuit 7 is provided with aheat storage tank 8 for thermally insulating (and storing) heat ofcooling water and an electromagnetic opening/closing valve 9 for openingand closing the sub cooling water circuit 7.

Next, the heat storage tank 8 is explained using FIG. 2.

The heat storage tank 8 comprises an inner cylinder 81 and an outercylinder 82 made of a material excellent in corrosion resistance such asstainless and formed into a bottomed cylindrical shape. The heat storagetank 8 has a structure in which end portions 8 a of the inner cylinder81 and the outer cylinder 82 are welded in a state in which the innercylinder 81 is accommodated within the outer cylinder 82, and athermally insulated space 83 substantially in a vacuum state is formedbetween the inner cylinder 81 and the outer cylinder 82. By the way, theinner cylinder 81 is integrally formed by a spinning process.

Within the inner cylinder 81, a storage section 811 for storing coolingwater is formed and the storage section 811 forms a columnar spaceextending in the vertical direction. Into a small diameter opening 812and a large diameter opening 813 of the inner cylinder 81 located at thelower portion of the storage section 811, a body 84 made of resin thatblocks both the openings 812 and 813 is inserted. By the way, a femalescrew formed in the large diameter opening 813 of the inner cylinder 81and a male screw formed at the body 84 are screwed with each other and,thereby, the inner cylinder 81 and the body 84 are joined together.

Between the inner cylinder 81 and the body 84, a ring-shaped rubberpacking 85 for sealing between the inner cylinder 81 and the body 84 isarranged. In more detail, the packing 85 is arranged at the boundarybetween the small diameter opening 812 and the large diameter opening813 in the inner cylinder 81.

In the body 84, a cooling water inflow channel 841 that causes the subcooling water circuit 7 on the opening/closing valve 9 side to becommunicated with the storage section 811 is formed. The end portion ofthe cooling water inflow channel 841 on the storage section 811 sideopens at the position in the vicinity of the small diameter opening 812of the inner cylinder 81, that is, at the lower position of the storagesection 811. The cooling water inflow channel 841 corresponds to theliquid inflow channel of the present invention.

To the end portion of the body 84 on the storage section 811 side, apipe 10 is attached. Then, through an in-body cooling-water-outflowchannel 842 formed in the body 84 and an in-pipe cooling-water-outflowchannel 101 formed in the pipe 10, the sub-cooling-water circuit 7 onthe water pump 4 side and the storage section 811 are communicated witheach other. The end portion of the in-pipe cooling water outflow channel101 on the storage section 811 side opens at the position in thevicinity of the top wall of the inner cylinder 81, that is, at theposition in the vicinity of the top end of the storage section 811. Thein-body cooling-water-outflow channel 842 corresponds to the liquidoutflow channel of the present invention.

To the end portion of the body 84 on the storage section 811 side, amixture prevention plate 11 having a substantially cup-like shape isattached so as to enclose the end portion of the cooling water inflowchannel 841 on the storage section 811 side. In the mixture preventionplate 11, a plurality of outflow holes 111 are formed and the coolingwater that has flowed in from the cooling-water-inflow channel 841 isguided to flow substantially evenly to the storage section 811 sidethrough the outflow holes 111.

An angle 12 is attached to the outer surface of the outer cylinder 82and the heat storage tank 8 is fixed to a vehicle by means of this angle12

Next, the operation of a cooling device having the above-mentionedconfiguration is explained below.

When the temperature of the cooling water becomes high, due to theoperation of the engine 1, the opening/closing valve 9 is opened and thehigh temperature cooling water is caused to flow into the heat storagetank 8. After the engine stops, the high temperature cooling water isthermally insulated and stored in the heat storage tank 8.

Then, when the engine is started, the temperature of the portion in thevicinity of the engine combustion chamber is raised by circulating thecooling water thermally insulated and stored in the heat storage tank 8through the engine 1.

Specifically, immediately before the engine is started, the water pump 4is put into operation and the opening/closing valve 9 is opened. Due tothis, the low temperature cooling water flows into the storage section811 of the heat storage tank 8 through the sub-cooling-water circuit 7and the cooling-water-inflow channel 841.

The cooling water that has flowed in pushes up the high temperaturecooling water thermally insulated and stored in the storage section 811and the high temperature cooling water circulates to the engine 1through the in-pipe cooling water outflow channel 101, the in-bodycooling water outflow channel 842, and the sub cooling water circuit 7.

At this time, the low temperature cooling water flowing into the storagesection 811 is designed to push up the high temperature cooling waterstored in the storage section 811 evenly with respect to the entirecircumference due to the effect of the mixture prevention plate 11.Therefore, the mixture of the low temperature cooling water flowing inand the stored high temperature cooling water is prevented and the hightemperature cooling water is caused to circulate to the engine 1.

Next, by using the ratio (D/H) between the inner diameter D of the innercylinder 81 (hereinafter, referred to as a tank inner diameter) and thelength H of the storage section 811 in the vertical direction(hereinafter, referred to as a tank height) as a parameter, the heatinsulation performance of the heat storage tank 8 is evaluated. Thedistance from the top end of the storage section 811, that is, from thetop wall of the inner cylinder 81, to the small diameter opening 812corresponds to the tank height H.

FIG. 3 shows the results of a study wherein the horizontal axisrepresents the ratio (D/H) between the tank inner diameter D and thetank height H. The vertical axis in FIG. 3 shows the average temperatureof the hot water in the heat storage tank 8 after the hot water at aninitial temperature of 90° C. is thermally insulated in the heat storagetank 8 for 24 hours.

The tank inner diameter D of the evaluated heat storage tank 8 is set toa constant value, that is, 100 mm, and the inner diameter of the smalldiameter opening 812 is also set to a constant value, and the tankheight H is changed.

As is obvious from FIG. 3, in the region in which D/H≦0.5 holds, thetemperature of the hot water after thermally insulated for 24 hours ishigh and high heat insulation performance can be obtained. This isbecause the storage section 811 is elongated in the vertical directionand the distance between the body 84, which is a main heat radiatingportion, and the hot water region (in the vicinity of the top end of thestorage section 811) is increased and the hot water region is extendedin the vertical direction. The ratio D/H may be set in order to satisfyseveral requirements for the heat storage tank such as an inner capacityof water and a vertical height that may be limited for installation ofthe storage tank on vehicles. In this aspect, the heat storage tank maybe designed to satisfy that the ratio D/H is equal to or greater than0.3. Instead, the ratio D/H may be set equal to or greater than 0.35.Further, the ratio D/H may be set equal to or greater than 0.4 in orderto satisfy an installation requirement. On the other hand, the ratio D/Hmay be set equal to or less than 0.45. Instead, the ratio D/H may be setequal to or less than 0.4 in order to improve hot water temperature.

While the invention has been described by reference to specificembodiments chosen for the purposes of illustration, it should beapparent that numerous modifications could be made thereto by thoseskilled in the art, without departing from the basic concept and scopeof the invention.

1. A heat storage tank comprising: an inner cylinder having a storagesection for storing liquid and an opening at a lower position of thestorage section; an outer cylinder accommodating the inner cylindertherein and forming a thermally insulated space between the innercylinder and the outer cylinder; and a body in which a liquid inflowchannel and a liquid outflow channel for causing the storage section tobe communicated with an outside are formed, the body blocking theopening, wherein an inner diameter of the inner cylinder is referred toas a tank inner diameter D, a length of the storage section in avertical direction is referred to as a tank height H in the heat storagetank in which the storage section is a columnar space extending in thevertical direction, and a ratio D/H satisfies the following: D/H≦0.5. 2.The heat storage tank as set forth in claim 1, mounted in a vehiclehaving a water-cooled internal combustion engine that is cooled bycooling water, wherein liquid stored in the storage section is coolingwater that has risen in temperature after cooling the water-cooledinternal combustion engine.